The invention relates generally to ultrasonic position determination in computer peripheral devices, and more specifically to an ultrasonic wireless pen system and method for providing pen-based input to a computerized system.
Computers rely on user input and interaction to provide data and to control their operation. This input is, in the case of today""s typical personal computer systems, provided via many different types of peripheral input devices. Such devices include keyboards which allow a user to type text that is then provided in electronic form to the computer, include mice which allow a user to provide coordinate information and switch actuated input to the computer by moving a mouse and depressing its buttons, and include more specialized devices such as graphics tablets that enable a user to draw with a special pen on a graphics tablet to provide coordinate and pressure information to the computer.
Keyboards are efficient for providing text data to computers for those with adequate typing skill and that need to input a large amount of text. But, efficient use of a keyboard requires special knowledge that must be obtained by practice, making the keyboard undesirable even as a method for text entry for those with poor typing skills. Inputting graphical or coordinate information via a keyboard is also quite difficult even for the skilled, as the data must be entered by depressing keys on the keyboard such as by entry of text representing the graphic or by use of cursor keys to provide position information.
Mice do a much better job of facilitating input of position information, and are commonly used to operate graphical interfaces to software and to draw or position objects on a computer screen. Movement of a mouse on a solid surface results in transmission of coordinate information that reflects the mouse""s movement to the computer, such that the computer can use the data to perform functions such as drawing an object or positioning a cursor. Depressing buttons on a mouse also provides a signal to the computer, which is used for functions such as to indicate selection of an object currently under a cursor on a computer screen. But, a mouse cannot easily be used to input text information, and a mouse is not as easy to draw with as are common noncomputerized items such as pens and pencils.
Use of a graphics tablet with a special pen enables the user to simulate use of a common writing utensil such as a traditional pen or pencil with which the user is comfortable, and so does not require adapting to peculiarities of devices used only in a computer context such as a mouse. A pen is also more versatile than either a mouse or a keyboard, as it allows easy entry of both graphic or positioning information such as a freehand sketch, and allows entry of text such as may be derived via a user""s handwriting with the pen.
But, pen systems such as the graphics tablet described above require a high degree of accuracy in position determination to be practical, so that a user does not have to correct or edit data input with such a pen before it can be used. Also, the pen device should not be cumbersome or complex to use, as the goal is to provide users with a simple and easy method of entering data into a computer.
What is needed is a method and apparatus that enable accurate position determination of a pen-like computer input peripheral device, which is both convenient to use and is reliably accurate.